Investigations are proposed to study the structure of the gramicidin channel in a model biological membrane, sonicated lecithin bilayer vesicles. Proton nuclear magnetic resonance (NMR) spectroscopy will be used to observe gramicidin resonances in the presence of phospholipid signals which are attenuated by perdeuteration. The synthesis of phospholipids with perdeuterated head group, glyceryl backbone and hydrocarbon side chains will be developed. The location of tryptophanyl residues in the gramicidin channel will be determined from fluorescence quenching measurements. These studies will help to characterize this particular ion-translocating channel and should also clarify the nature of the interactions which occur between polypeptides and phospholipids in a biological membrane.